The prudent keep their knowledge to themselves, but a fool’s heart blurts out folly.
NMVA prudent man conceals knowledge: but the heart of fools proclaim foolishness.
OJBA prudent man concealeth da'as, but the lev kesilim (mind of fools) preaches folly.
T4TThose with good sense do not reveal all that they know; foolish people show clearly by what they say that they ◄are ignorant/have not learned much►.